Document FR-A-2 759 333 describes an example of such a seat which is satisfactory but whose pivot mechanism is more specifically designed to be manually operated.
However, electrical operation of a pivot mechanism of this type gives rise to a problem if it is desirable to mount the electric motor activating the pivot mechanism on the first part of the seat (especially if said first part is the seat part of the seat).
In effect, the control shaft is not fixed relative to the first part of the seat but instead is subjected to a nutating movement, i.e. not only does it rotate on itself about its central axis, there is also circular movement of said central axis in translation.
This nutating motion is not compatible with providing a simple mechanical connection between the control shaft and the electric motor.